BLOOD SUPPLY OF THE PENIS Is from the internal pudendal artery, which enters the perineum through Alcock’s canal and gives rise to 4 terminal branches 1. Dorsal art. supplies penile skin and glans and contributes little to erectile function 2. Cavernosal art. within the corpora, branches into helicine arterioles 3. Bulbar art. 4. Scrotal art.
BLOOD SUPPLY OF THE PENIS• Venous drainage is both intra + extra cavernosal Intracavernosal drainage: helicine arterioles drain into vascular lacunar spaces of corp. cavernosum which empty into subtunical v. emissary v., pierce tunica albuginea deep dorsal v.
BLOOD SUPPLY OF THE PENIS Extracavernosal drainage: is via 3 routes1. Deep dorsal v. – drains distal corpora into santorini’s vesicoprostatic venous plexus2. Cavernosal and crural v. – drains prox. corpora into santorini’s plexus and int. pudendal v.3. Superficial dorsal v. – drains blood from penile skin, glans and communicates with deep dorsal v.
NERVE SUPPLY OF THE PENIS Autonomic Paraympathetic nerves from S2-4 nerve roots primarily control erectile function while the sympathetic nerves from T11-L2 control detumescence and also contribute to ejaculation and emission. These autonomic nerve fibers form the pelvic plexus of nerves and enter the penis within the cavernosal nerves that course lateral and inferior to the prostate. N.B. It is these nerves that are preserved during nerve sparing radical prostatectomy.
NERVE SUPPLY OF THE PENIS Somatic Peripheral nerves (dorsal penile and pudendal n.) form sensory and motor elements through a reflex arc in the sacral spinal cord at Onufs nucleus (S2-4). Peripheral nerves containing sensory elements are also responsible for erectile function, as they innervate the ischio and bulbo cavernosus muscles of the penis
NERVE SUPPLY OF THE PENIS Central Ultimate central nervous system control is likely initiated in the hypothalamus in the medial pre-optic area that integrates psychological and tactile stimuli.
TYPES OF ERECTIONReflexogenic erection:A genital stimulation leads to a reflexogenic erection. Afferent signal pass via the pudendal nerve to the sacral erection center, this sends the efferent signal via the inferior hypogastric plexus. The reflexogenic erection is largely independent of cortical influences, as this kind of erection can remain intact after cervical or thoracic spinal cord injuries.
Psychogenic erection: The cortical processing of sensory, visual, auditory stimuli or fantasies are triggers for an erection. The cortical centers influence the sacral erection centers, which cause the erection via activation of the inferior hypogastric plexus.
Nocturnal erection: Occurs during the REM sleeping phase and can be measured during sleeping studies (Nocturnal penile tumescence = NPT). Typical for the psychogenic impotence is the existence of NPT, in contrast to serious vascular erectile dysfunction. Sympathetic centers mediate nocturnal erections, the existence of NPT still cannot rule out damage to the sacral parasympathetic erection center.
REVIEW MECHANISM OF ERECTION:What happens to the penis during arousal? Audiovisual or tactile stimuli activate nuclei of spinal erection center T11-L2 and S2-4• Signals relayed viacavernosal n. to erectiletissue of corpora cavernosaactivating the veno-occlusivemechanism
• This triggers increased arterial blood flowinto sinusoidal spaces, relaxation ofcavernosal smooth muscle, and opening ofvascular spaces
The result: Blood expands the sinusoidal spaces which compresses the subtunical venous plexuses against the tunica albuginea decreasing the venous outflow, and further compressing the emissary veins
Excitatory stimuli from the CNS produce erections through a variety of neurotransmitters. Many neurotransmitters including acetylcholine (ACh) and vasoactive intestinal polypeptide (VIP) contribute to erectile function. The most important neurotransmitter in the corpora cavernosa is nitric oxide (NO).
Following sexual stimulation, acetyl choline triggers the release of nitric oxide from endothelial cells, and diffuses into the corporal smooth muscle. Nitric oxide (NO) is a gas that acts as a vasodilating agent, inducing smooth ms relaxation via (guanylate cyclase) the cGMP system. Therefore, NO arteries dilate fills the corpora spongiosum and cavernosa with blood = erection
cGMP is broken down by phosphodiesterase type 5 (PDE5). When this occurs the Ca2+ increases in concentration in the cell, resulting in contraction of the smooth muscle cells and detumescence. N.B. Sildenafil (Viagra) is a PDE5 inhibitor, and allows for erections to be maintained in response to stimuli, but does not initiate erection.
ERECTION VS. DETUMESCENCE Stimulation of the pelvic plexus and the cavernous nerves (Parasympathetic fibers ) through tactile sensory stimuli to the penis, releases acetylcholine, which enhances penile blood flow and smooth muscle relaxation, thus inducing erection Sympathetic (adrenergic) fibers and norepinephrine neurotransmission help to maintain the penis in its flaccid state. norepinephrine, activates alpha-adrenergic receptors that produce vasoconstriction of the penile vasculature and decompression of penile venules, which result in detumescence.
PHASES OF ERECTIONPhase Term Description 0 Flaccid phase Cavernosal smooth ms contracted; sinusoids empty; minimal arterial flow 1 Latent (filling) Increased pudendal artery flow; penile phase elongation 2 Tumescent phase Rising intracavernosal pressure; erection forming 3 Full erection Increased cavernosal pressure (100 mmHg) phase causes penis to become full erect 4 Rigid erection Further increases in pressure (to several phase hundred mmHg) + ischiocavernosal muscle contraction 5 Detumescence Following ejaculation, sympathetic discharge phase resumes; there is smooth muscle contraction and vasonstriction; reduced arterial flow; blood is expelled from sinusoidal spaces
SO WHAT IS IMPOTENCE OR ERECTILEDYSFUNCTION?The persistent inability to achieve or maintain a penile erection sufficient for sexual intercourse
ED affects about 10% of men aged 40-70 years, and prevalence increases with age Primary ED (ie, the man has never been able to attain or sustain erections) is rare and is almost always due to psychologic factors (guilt, fear of intimacy, depression, severe anxiety) or clinically obvious anatomic abnormalities. Most often, ED is secondary (ie, a man who previously could attain and sustain erections no longer can). Over 80% = have an organic etiology. However, in many men with organic disease, ED leads to secondary psychologic difficulties that compound the problem.What is the aetiology of ED?
ED is more prevalent among patients with atherosclerotic peripheral vascular disease, hypertension, diabetes mellitus (75% of diabetic pts), hypercholesterolemia, and heart disease and among men who smoke cigarettes.Psychogenic ED Organic EDED caused exclusively by Caused exclusively byemotional stress or psychiatric vascular, neurologic,disease = 10% - 50% of all endocrine, or other physicalcases disease = 50% - 80% In the majority of impotent men, erectile impairment has both a psychological and an organic basis.
How to diagnose & evaluate ED? History Examination Investigation
HISTORY Sexual Some symptoms suggest psychogenic ED, and others suggest organic disease. A psychogenic cause is suggested by the sudden onset of ED or the presence of ED under some circumstances but complete erection at other times. In contrast, gradual deterioration of erectile quality over months or years with preservation of libido suggests organic disease. Psychological Evaluation
HISTORY Medical Inquiries should be made about: DM, HTN, smoking, hypercholesterolemia, and hyperlipidemia as well as about liver, renal, vascular, neurologic, psychiatric, and endocrine disease. Surgical History Abdominal, pelvic, perineal Drug History Androgenic substances are associated with decreased serum testosterone levels and decreased libido.
EXAMINATION Full Physical Body habitus, 2ndry sexual characteristics CVS, abdomen, neurological (bulbocavernosus reflex is used to assess integrity of S2-4) External Genitalia Penis: Phimosis, penile lesions Testis: size, consistency DRE
INVESTIGATION Specialized Evaluations: Indicated for failure of ttt, peyronie’s disease, 1ry ED, history of surgery/trauma, complicated endocrine or neuropsychiatric disorderA. Vascular EvaluationB. Neurologic EvaluationC. Psychologic EvaluationD. Hormonal Evaluation
1st line vascular evaluation: Intracavernosal injection Allows bypass of neurologic and hormonal influences, directly evaluates penile blood flow Alprostadil (10 – 20 μg) alone, or a combination of papaverine + phentolamine (ie Bimix), or all three (ie Trimix). Compress needle site manually to prevent hematoma
2nd line vascular evaluation: Duplex U/S: measures penile blood flow; most reliable and least invasive assessment of ED Color Doppler U/S: measures arterial peak systolic velocity value (N:>35 cm/s) and end diastolic velocity (N:<5 cm/s) Cavernosography: measures penile blood flow following intracavernosal inj of contrast and induction of artificial erection. Can identify venous leakage.
Venous leak (veno-occlusive insufficiency).Bilateral (a and b) Doppler waveforms of the cavernosal arteries at 25 min post-injection of prostaglandin E demonstrate a high peak systolic velocity (>40 cm/s), which excludes arterial insufficiency as a cause of erectile dysfunction in this patient.However, a persistent diastolic flow velocity of more than 5 cm/s is suggestive of venous leak.
2nd line vascular evaluation: Selective Penile Arteriography: to specifically assess a defective/ruptured branch of cavernous art.A. Arterial phase of right pudendal arteriography demonstrating obviousextravasation (arrow) at right penile artery.B. Venous phase image of right pudendal arteriography demonstratingexpansion of extravasation (arrow) and opacified penile veins.
TREATMENT Psychosexual therapy Aims to understand and address the underlying psychological issues following proper evaluation Instructs the pt on information regarding sex education, partner communication and sexual behavioral therapy
TREATMENT Oral Medication PDE5 (phosphodiesterase type-5) inhibitors (ex. Sildenafil = viagra, tadalafil = cialis, vardenafil = levitra) Blocks the breakdown of cGMP, thus maintaining erection Sexual stimulation is still needed to initiate erection Adverse Effects: headache, visual disturbance Contraindication: pts on nitrates, recent MI, recent stroke, unstable angina
TREATMENT Androgen Replacement Therapy: indicated for hypogonadism. Available in oral, IM, patch & gel forms. In older men, PSA must be checked before and during ttt. Intraurethral pellet therapy: using a synthetic PGE-1 pellet administered into the urethra. Unavailable in Egypt. Intracavernosal therapy: Alprostadil/Caverjet (synthetic PGE1) enhances cavernosal smooth muscle relaxation. The needle is inserted at right angles into the corpus cavernosum on the lateral aspect of the penile shaft. A/E = priapism, pain, hematoma
TREATMENT Alternative therapy Vacuum erection device: uses vacuum chamber, pump and constriction device to increase blood flow into the penis and maintain rigidity via constriction band
TREATMENT Alternative therapy Penile prosthesis: may be semi-rigid, malleable or inflatable. Inserted surgically into the corpora to provide sufficient size & rigidity for sexual intercourse. A/E = erosion, infection, mechanical failure